Method of treating mercury contaminated surfaces



Patented June 1, 1943 METHOD OF TREATING MERCURY CON- TAMINATED SURFACESMerle Randall, Berkeley, Calif.

No Drawing. Application March 26, 1942, Serial No. 436,247

11 Claims. (Cl. 1l7l21) This invention relates to a method of treatingsurfaces of rooms, furnace rooms, and other closed and semi-clsedspaces, the walls of which have become contaminated with liquid metallicmercury.

an important object of my invention is to make it possible to decreasethe health hazard in rooms, furnace rooms and other closed andsemi-closed spaces, the walls of which are contaminated with liquidmetallic mercury.

Another important object of my invention is to provide a process wherebythe concentration of mercury vapor in rooms, furnace rooms, and closedand semi-closed spaces. the Walls of which contaminated with metallicmercury, may be conveniently reduced.

Another object of my invention is to provide such a process that isapplicable under acid conditions as well asunder the neutral or alkalineconditions, to which the process of my copending application Serial No.399,417, filed June 23, 1941, is limited.

An important additional object of my invention is to provide a processfor the treatment of mercury contaminated surfaces which cannot betreated by the process of my copending application No. 399,417 wherebecause of aesthetic reasons a better appearance is desired than thatresulting from that process.

Other objects and advantages of my invention will be evident from thefollowing description.

In my copending application Serial No. 399,417, 1 disclose the method oftreating mercury mines which comprises spraying the walls, muck piles,timbers, stopes, tunnels, and other parts of the mercury mine which arecontaminated with free metallic mercury with a water solution of analkali polysulfide. Certain additional materials which are valuableadditions to the alkali polysulfide are also disclosed.

While the method disclosed in my aforesaid copending application isentirely satisfactory in the majority of mercury mines, some situationsprevail where the mercury contaminated surfaces are acidic in nature,and under these conditions alkali polysulfides cannot be used becausepoisonous hydrogen sulfide would be formed. There are also othersituations where for appearance or processing reasons a more permanentcoating is desired, or where alkali polysulfide solutions are notallowable.

I have found that a coating containing a. substantial amount ofdissolved free sulfur or an excess of free elemental sulfur issatisfactory for the treatment of mercury contaminated surfaces,

and that the health hazard in moderately ventilated rooms or closedspaces, the surfaces whereof are contaminated with metallic liquidmercury, and which have been so coated is satisfactorily reduced.

If the surface of a closed space is impregnated with liquid mercury thenan increase in the rate of ventilation may not suffice to decrease theconcentration of mercury vapor in the closed space below the allowablesafe limit. However, if the large surface of the many small mercurydroplets is coated over by a coating containing substantial amounts ofdissolved sulfur or an excess of finely divided elementary sulfur, therate of diffusion of mercury through the film into the air or gas comingin Contact with the coating is very low and some mercury in the air orgas so coming in contact with the coating reacts with the sulfur thusforming harmless mercuric sulfide.

The dissolved sulfur may be dissolved in the vehicle of the coating ormay be in the form of alkali polysulfide when acidic conditions are notencountered. The coating may be applied by spraying, brushing, or anyother suitable means. A hand brush, a so-called air brush, a paintspray, a spray nozzle, or other similar means may be used.

Any coating containing substantial amounts of free sulfur in solution orin suspension i useful, but dissolved sulfur in the form of an alkalipolysulfide should not be used if acid conditions are present.

In this specification and in the appended claims I have used the termfree sulfur to include solid elemental sulfur and also elemental sulfurdissolved in a solvent.

One form of my invention comprises coating over the mercury contaminatedsurface by brushing by means of a hand brush with an oil paintcontaining substantial amounts of added wettable sulfur. The coating mayalso be applied by using a paint spray.

As an example of this form of my invention, ten per cent of finelydivided sulfur is added to an oil paint and the same applied as acoating over the mercury contaminated surface.

There is a small vapor pressure over solutions containing substantialamounts of dissolved sulfur or over solid sulfur which assists inreducing the concentration of mercury in the space contained within thecoated contaminated surfaces.

Another form of my invention which is adapted to be used in spaces otherthan mines and where the conditions are alkaline or neutral comprisescoating over the mercury contaminated surface with a water solution ofdissolved sulfur in the form of alkali polysulfide (sulfur dissolved inalkali hydroxide) which preferably contains wettable sulfur, wettingagents, and adhesives as disclosed in my copending application SerialNo. 399,417.

Another form of my invention applicable to non-acid conditions comprisescoating over the mercury contaminated surfaces with a coating 01 thecalcimine or lralsomine type containing substantial amounts of colloidalor finely divided free sulfur.

As an example of this form of my invention the mercury contaminatedsurfaces are coated by spraying by means of a paint spray with akalsomine paint containing ten per cent by weight of the kalsomine offinely divided sulfur added to the paint mix.

Another form of my invention comprises coating over the mercurycontaminated surface with any form of coating and then dusting thesurface with finely divided sulfur while the film is still in the tackyor sticky condition. 'The coating may or may not contain dissolvedsulfur or added finely divided sulfur, but coatings containing such.added elemental sulfur are preferred for dusting with finely dividedsulfur. As an example of this form of my invention a mercurycontaminated surface is coated by brushing with an oil paint, and thenas the paint dries to the sticky condition finely divided elementalsulfur is dusted on with a dust gun such as is used for applying able tothe treatment of mercury contaminated mines with acidic conditions orother surfaces with acidic conditions comprises coating the surfaceswith coatings containing the sulfur preferr ably dissolved in neutral ornon-alkaline solvents.

Whether a solution of free sulfur in an alkaline solvent, in a neutralsolvent, or in a non-alkaline solvent, an oil paint with substantialamounts of added sulfur, a coating with free sulfur dusted on, or anyother embodiment of my invention, is to be used will depend largely uponthe degree of acidity or alkalinity of the surface to be treated andupon the appearance desired and upon other practical requirements of theuse.. to which the mercury contaminated surface to be treated is to beput. Such choice of the particular embodiment of my invention may bemade by any operator reasonably skilled in the art.

The method of treatment with a coating containing free sulfur will avoidcontamination of the contained space from the mercury contaminatedsurfaces, and will assist in reducing the mercury concentration in theclosed space. With moderate ventilation the mercury concentration can belowered to remove the health hazard. If the surface is exposed forperiods of time to currents of air or gas containing mercury vapor abovethe saturation vapor pressure of mercury at the temperature of thesurface. then the surface must be rccoated to provide the maximum prtection.

From the foregoing description, the uses, advantages, and operation ofmy invention will be readily understood by those skilled in. the art towhich the invention appertains. While I have described certain examplesof my invention, I desire to have it understood that the examples givenare merely illustrative. and that the invention is not, to be limited tothe details disclosed herein, but is to be accorded the full scope ofthe appended claims.

I claim:

1. A method of treating mercury contaminated surfaces comprising coatingsaid surfaces with a composition containing free sulfur.

2. A method of treating mercury contaminated surfaces comprising coatingsaid surfaces with a composition containing free sulfur in solution inthe vehicle of the coating composition.

3. A method of treating mercury contaminated surfaces comprising coatingsaid surfaces with a composition containing wettable sulfur.

4. A method of treating mercury contaminated surfaces comprising coatingsaid surfaces with a coating composition and then dusting sulfur on saidcoating.

5. A method of treating mercury contaminated surfaces comprising coatingsaid surface with an oil paint containing a substantial amount of freesulfur.

6. A method of treating mercury contaminated surfaces comprising coatingsaid surfaces with a coating composition, and then adding finely dividedsulfur to said coating while said coating is still in the adhesivecondition.

7. A method of treating mercury contaminated surfaces comprising coatingsaid surfaces with an oil paint containing a substantial amount of freefinely divided sulfur.

8. A method of treating mercury contaminated surfaces comprising coatingsaid surface with a coating of the kalsomine type containing an excessof finely divided sulfur.

9. A method of treating mercury contaminated surfaces suitable for usein non-acid conditions comprising coating said surfaces with acomposition containing substantial amounts of free sulfur dissolved inan alkaline solvent.

10. A method of treating mercury contami nated surfaces suitable for usein non-acid conditions comprising coating said surfaces with acomposition containing substantial amounts of free sulfur dissolved incalcium hydroxide.

11. A method of treating mercury contaminated surfaces comprisingcoating said surfaces with a coating composition containing elementalsulfur, and then dusting finely divided sulfur on said coating whilesaid coating is still in the adhesive condition.

MERLE RANDALL.

